Method for automatically controlling composition of chemical copper plating solution

Abstract

The pH of a chemical copper plating solution is exactly measured for a prolonged time by utilizing a copper oxide prepared by etching metallic copper in an 0.1-1 N inorganic acid then oxidizing the etched metallic copper in an aqueous 0.1-1 N alkali metal hydroxide solution as a main electrode for pH measurement or reducing agent concentration measurement in terms of pH. A combination of the pH measurement with well known procedures for measuring concentrations of cupric ions and a complexing agent exactly measures the pH and the concentrations of a reducing agent, cupric ions and a complexing agent for a continuation of longer time than the conventional procedures.

What is claimed is: 
     
       1. A method for controlling a composition of a chemical copper plating solution, which comprise leading a predetermined amount of a chemical copper plating solution sampled from a plating tank to a main electrode chamber of a pH detection cell comprising a main electrode chamber with a copper oxide electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber, detecting a difference in potential between the copper oxide electrode and the reference electrode, and transmitting the difference as a signal from a pH controller when the detected potential is smaller than a present potential in the pH controller as an absolute value, thereby supplementing the chemical copper plating solution with a pH makeup solution until the detected potential exceeds the preset potential, and thereby keeping the pH of the chemical copper plating solution continuously constant. 
     
     
       2. A method according to claim 1, wherein the copper oxide electrode is an electrode prepared by etching metallic copper in 0.1-1 N hydrochloric acid, sulfuric acid or nitric acid and then oxidizing the etched metallic copper in an aqueous 0.1-1 N caustic soda or caustic potash solution, the reference electrode is a silver-silver chloride electrode, and the reference electrode solution is an chlorine ion-containing solution. 
     
     
       3. A method for controlling a composition of a chemical copper plating solution, which comprises leading a predetermined amount of a chemical copper plating solution sampled from a plating tank to a main electrode chamber of a pH detection cell comprising a main electrode chamber with a copper oxide electrode, a reference electrode chamber with a reference electrode, and a membrane provided between both chambers, whereas leading a reference electrode solution to the reference electrode chamber, detecting a difference in potential between the copper oxide electrode and the reference electrode by a pH controller, transmitting the difference as a signal from the pH controller when the detected potential is smaller than a preset potential in the pH controller as an absolute value, thereby supplementing the chemical copper plating solution with a pH-adjusting solution until the detected potential exceeds the preset potential, and thereby keeping the pH of the chemical copper plating solution continuously constant, adding a sulfite ion containing solution to the sampled solution leaving the main electrode chamber of the pH detection cell, then leading said solution to a main electrode chamber of a reducing agent concentration detecting cell comprising a main electrode chamber with a copper oxide electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, whereas leading a reference electrode solution to the reference electrode chamber of the reducing agent concentration detection cell, detecting a difference in potential between the copper oxide electrode and the reference electrode, transmitting the difference as a signal from a reducing agent concentration controller when the detected potential is smaller than a preset potential in the reducing agent concentration controller as an absolute value, thereby supplementing the chemical copper plating solution with a reducing agent makeup solution until the detected potential exceeds the preset potential, and thereby keeping the reducing agent concentration of the chemical copper plating solution continuously constant. 
     
     
       4. A method according to claim 3, wherein the copper oxide electrodes for the pH detection cell and the reducing agent concentration detection cell are electrodes prepared by etching metallic copper in 0.1-1 N hydrochloric acid, sulfuric acid or nitric acid and then oxidizing the etched metallic copper in an aqueous 0.1-1 N caustic soda or caustic potash solutin, the reference electrodes for the pH detection cell and the reducing agent detection cell are silver-silver chloride electrodes, and the reference electrode solutions are an chlorine ion-containing solution. 
     
     
       5. A method for controlling a composition of a chemical copper plating solution, which comprises leading a predetermined amount of a chemical copper solution sampled from a plating tank to a main electrode chamber of a pH detection cell comprising a main electrode chamber with a copper oxide electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber, detecting a difference in potential between the copper oxide electrode and the reference electrode, transmitting the difference as a signal from a pH controller when the detected potential is smaller than a preset potential in the pH controller as an absolute value, thereby supplementing the chemical copper plating solution with a pH-adjusting solution until the detected potential exceeds the preset potential, and thereby keeping the pH of the chemical copper plating solution continuously constant, adding a Cu +2  ion containing solution to the sampled solution leaving the main electrode chamber of the pH detection cell, then leading said solution to a main electrode chamber of a cupric ion concentration detection cell comprising a main electrode chamber with a non-soluble electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, while leading a reference electrode solution to the reference chamber of the cupric ion concentration detection cell, detecting a difference in potential between the non-soluble electrode and the reference electrode, transmitting the difference as a signal from a cupric ion concentration controller when the detected potential is smaller than a preset potential in the cupric ion concentration detector, thereby supplementing the chemical copper plating solution with a cupric ion-adjusting solution until the detected potential exceeds the preset potential and thereby keeping the cupric ion concentration of the chemical copper plating solution cintinuously constant, adding a triethylenetetramine containing solution and a Fe +3  ion containing solution to the sampled solution leaving the main electrode chamber of the cupric ion detection cell, then leading said solution to a main electrode chamber of a complexing agent concentration detection cell comprising a main electrode chamber with a non-soluble electrode, a reference electrode chamber with a reference electrode, and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber of the complexing agent concentration detection cell, detecting a difference in potential between the non-soluble electrode and the reference electrode, and transmitting the difference as a signal from a complexing agent concentration controller when the detected potential is higher than a preset potential in the complexing agent concentration controller, thereby supplementing the chemical copper plating solution with a complexing agent-adjusting solution until the detected potential becomes lower than the preset potential, and thereby keeping the complexing agent concentration of the chemical copper plating solution continuously constant. 
     
     
       6. A method according to claim 5, wherein the copper oxide electrode for the pH detection cell is an electrode prepared by etching metallic copper in 0.1-1 N hydrochloric acid, sulfuric acid or nitric acid and then oxidizing the etched metallic copper in an aqueous 0.1-1 N caustic soda or caustic potash solution, the reference electrodes for the pH detection cell, the cupric ion concentration cell and the complexing agent concentration cell are silver-silver chloride electrodes, and the references electrode solutions are a chlorine ion-containing solution. 
     
     
       7. A method for controlling a composition of a chemical copper plating solution, which comprises leading a predetermined amount of a chemical copper plating solution sampled from a plating tank to a main electrode chamber of a pH detection cell comprising a main electrode chamber with a copper oxide electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber, detecting a difference in potential between the copper oxide electrode and the reference electrode, transmitting the difference as a signal from a controller when the detected potential is smaller than a preset potential in the pH controller as an absolute value, thereby supplementing the chemical copper plating solution with a pH-adjusting solution until the detected potential exceeds the preset potential and thereby keeping the pH of the chemical copper plating solution continuously constant, adding a Cu +2  ion containing solution to the sampled solution leaving the main electrode chamber of the pH detection cell, then leading said solution to a main electrode chamber of a cupric ion concentration detection cell comprising a main electrode chamber with a non-soluble electrode, a reference electrode chamber with a reference electrode, and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber of the cupric ion concentration cell, detecting a difference in potential between the non-soluble electrode and the reference electrode, transmitting the difference as a signal from a cupric ion concentration controller when the detected potential is smaller than a preset potential in the cupric ion concentration controller, thereby supplementing the chemical copper plating solution with a cupric ion-adjusting solution until the detected potential exceeds the preset potential and thereby keeping the cupric ion concentration of the chemical copper plating solution continuously constant, adding a sulfite containing solution and an iodine ion containing solution to the sampled solution leaving the main electrode chamber of the cupric ion detection cell, then leading said solution to a main electrode chamber of a reducing agent concentration detection cell comprising a main electrode chamber with a copper oxide electrode or non-soluble electrode, a reference electrode chamber with a reference electrode, and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber of the reducing agent concentration detection cell, detecting a difference in potential between the copper oxide electrode or non-soluble electrode and the reference electrode, transmitting the difference as a signal from a reducing agent concentration controller when the detected potential is smaller than a preset potential in the reducing agent concentration controller as an absolute value, thereby supplementing the chemical copper plating solution with a reducing agent-adjusting solution until the detected potential exceeds the preset potential and thereby keeping the reducing agent concentration of the chemical copper plating solution continuously constant, adding a triethylenetetramine containing solution and a Fe +3  containing solution to the sampled solution leaving the main electrode chamber of the cupric ion detection cell, then leading said solution to a main electrode chamber of a complexing agent concentration detection cell comprising a main electrode chamber with a non-soluble electrode, a reference electrode chamber with a reference electrode and a membrane provided between both chambers, while leading a reference electrode solution to the reference electrode chamber of the complexing agent concentration detection cell, detecting a potential between the non-soluble electrode and the reference electrode, transmitting the difference as a signal from a complexing agent concentration controller when the detected potential is larger than a preset potential in the complexing agent concentration controller, thereby supplementing the chemical copper plating solution with a complexing agent-adjusting solution until the detected potential becomes lower than the preset potential, and thereby keeping the complexing agent concentration of the chemical copper plating solution continuously constant. 
     
     
       8. A method according to claim 7, wherein the copper oxide electrode for the pH detection cell and the reducing agent detection cell are electrodes prepared by etching metallic copper in 0.1-1 N hydrochloric acid, sulfuric acid or nitric acid and then oxidizing the etched metallic copper in an aqueous 0.1-1 N caustic soda or caustic potash solution, the reference electrodes for the pH detection cell, the reducing agent concentration detection cell, the cupric ion concentration detection cell and the complexing agent concentration detection cell are silver-silver chloride electrodes, and the reference electrode solutions are a chlorine ion-containing solution.